Sudden Gains in Cognitive-Behavioral Therapy for Seasonal Affective Disorder

Sudden gains are associated with better acute and follow-up outcomes in cognitive-behavioral therapy (CBT) for mood and anxiety disorders. Using the group CBT for seasonal affective disorder (CBT-SAD) condition (n=88) from a parent randomized clinical trial, this study examines whether sudden gains can be detected in CBT-SAD and whether they relate to outcome at post-treatment and at follow-ups one and two winters later. Applying Kelly et al.'s (2005) criteria to week-to-week symptom changes [i.e., scores on the Structured Interview Guide for the Hamilton Rating Scale for Depression-Seasonal Affective Disorder Version (SIGH-SAD)] with SIGH-SAD score drop ≥ 6, 44.3% (39/88) of CBT-SAD participants had a sudden gain. Most sudden gains (25/39, 64.1%) occurred between pre-treatment and Week 3. Sudden gainers had lower depression severity on the Beck Depression Inventory-Second Edition (BDI-II) and a greater likelihood of remission (BDI-II ≤ 8) at both winter follow-ups than non-gainers. Sudden gain groups did not differ on post-treatment depression outcomes. Relative to non-gainers, sudden gainers showed greater improvement in seasonal beliefs, CBT-SAD's potential mechanism, during CBT-SAD, with more flexible seasonal beliefs than non-gainers at post-treatment. Membership in a particular CBT-SAD group was not related to the effect of sudden gains on treatment outcome.